Bubble sizes in the water measured during the high-Arctic ASCOS expedition 2008

Sarah Norris

Upper ocean gas bubbles generate airborne droplets when they burst at the surface, either "film droplets", from remnants of the surface of a bubble, or "jet droplets", formed by a jet of liquid that shoots upward from the bottom of the bubble as its upper rim breaks the surface. When droplets evaporate, insoluble material from the upper ocean contained inside the droplets will remain airborne as aerosol particles. This is a well-known mechanism whereby, for example, breaking wind waves generate sea-salt aerosols. In the Arctic summer, with short fetch over open water and relatively low wind speeds, it is not obvious that bubbles will form. Hence, during ASCOS we deployed a system to measure number and size of bubbles in the upper water column.

References

Data description

This file contains the standard bubble spectra as matlab structure.
A 2 minute averaged spectra was recorded every 15 minutes while the open lead site was manned.
The time stamp is for the start of the two minute averging period.

Instrument: The Mini-Bubble measuring system (owned by Gerrit de Leeuw, Helsinki).
It provides 20 size bins between 30 and 1500micrometer diameter.

Comments

Gas bubbles formed in the upper ocean will generate droplets in the air above the surface when they burst. Two types of droplets are generated; so-called film droplets which is the remnants of the inner surface of the bubble, and so-called jet droplets which are formed by the (due to the pressure difference) jet of liquid that shoots upward from the bottom of the bubble as its upper rim breaks the surface. Both types of droplets may evaporate and what soluble or insoluble material that might be in the droplets, emanating from the upper ocean surface, will remain airborne as an aerosol. This is a well-known mechanism whereby, for example. Breaking wind waves generate so-called sea-salt aerosols. In the Arctic, with short fetch over open water, it is not obvious that bubbles will form; hence during ASCOS we deployed in the upper water column a system to measure number and size of bubbles.